Common Name: Annual Yellow Sweetclover

General Information

Melilotus indicus is an annual plant with an erect stem that branches from the base; it can grow around 100cm tall[].
The plant is sometimes harvested from the wild as a local source of food, medicines and as an insect repellent. It has been used as a green manure.
The plant can escape from cultivation and become a weed[].

Known Hazards

The plant contains coumarin, a substance produced by the plant because it acts as an appetite suppressant and gives some protection from grazing - it is also the compound that gives some dried plants the smell of new mown hay. Coumarin is found naturally in many fruits, including strawberries, black currants, apricots, and cherries; it also has some medicinal applications, though it is also known to be toxic, affecting especially the liver and kidneys. Coumarin is of relatively low toxicity to humans – indeed it has often been used as a flavouring and aromatic additive in foods and other commodities. However, it can be much more toxic to other species, especially rodents and specifically rats.
The fresh plant material, consumed in moderation, is generally safe. However, the dried plant material, especially if it is not dried properly and is invaded by fungi, is potentially much more toxic as the coumarin breaks down to form other compounds that can have a strongly anticoagulant effect upon the blood. Warfarin, a well-known anticoagulant drug and rat poison, is one of those compounds produced from coumarin.

Botanical References

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Range

Mediterranean region - Portugal to Turkey and the Levant, Morocco to Egypt; east to western China. The Himalayas and Arabia

Habitat

A weed of fields, waste places and irrigated crops, also found near waterbodies, in river valleys, on seaside sands, in inhabited areas, roadsides, on exposed stony-debris slopes[, ]. Open places, alkaline soils of meadow, and roadsides[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual
Height	1.00 m
Pollinators	Bees
Cultivation Status	Cultivated, Wild

Cultivation Details

Melilotus indicus is a plant of the warm temperate zone to the tropics, where it is found at elevations up to 1,650 metres. It grows best in areas where annual daytime temperatures are within the range 15 - 25°c, but can tolerate 4 - 28°c[]. When dormant, the plant can survive temperatures down to about -2°c, but young growth can be severely damaged at -1°c[]. It prefers a mean annual rainfall in the range 600 - 900mm, but tolerates 250 - 1,300mm[].
Prefers a sunny position, but tolerates light shade[]. Plants can tolerate moderate levels of salt in the soil[]. Prefers a pH in the range 6.5 - 7, tolerating 5 - 8.5[].
This species is often cultivated as a fodder crop and cultivars low in coumarin have been developed[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[]. When removing plant remains at the end of the growing season, it is best to only remove the aerial parts of the plant, leaving the roots in the ground to decay and release their nitrogen.

Edible Uses

Leaves - cooked[].

Medicinal

The seed is made into a gruel and used in the treatment of bowel complaints and infantile diarrhoea[, ].

The plant is discutient, emollient, astringent, strongly laxative and narcotic[, , ]. A decoction is used externally as a disinfectant wash to bathe infections[]. The plant is made into a poultice or plaster and applied to swellings[, ].

The plant contains coumarin, which is an anticoagulant[]. The coumarin found in plants does not have anticoaggulant activity, it is the various compounds derived from coumarin that are used in this way. Simply drying the plant will not necessarily produce these compounds[].
The plant also contains dicumarol, which is a broad spectrum bactericide[].

Agroforestry Uses:

The plant has been grown as a green manure[].

Other Uses

The leaves repel insects. They have been placed in beds to repel bedbugs[].

Propagation

Seed - sow spring to mid-summer in situ[]. Pre-soaking the seed for 12 hours in warm water will speed up the germination process, particularly in dry weather[]. Germination will usually take place within 2 weeks.